Historically, plant tissue culturing techniques have been employed primarily as a method of asexual propagation. These techniques allowed the rapid proliferation of plant lines. It was generally believed that all plants arising from a tissue culture would be genetically identical to the parental plant. While phenotypic variants were frequently observed among regenerated plants, their presence was considered undesirable to the goal of plant propagation and thus were generally ignored or discarded.
More recently, the potential of plant tissue culture techniques as a tool in the development of new plant varieties has been appreciated. See, e.g., Larkin and Scowcroft, (1981) Theor. Appl. Genet. 60: 197-214; Sibi et al., U.S. Pat. No. 4,003,156. Rather than ignore the variant plants developed from tissue cultures, it was observed that tissue culturing per se apparently led to phenotypic variants. While this variation associated with tissue culturing has been observed in a wide variety of species, the mechanism of the variations has not been elucidated.
The propagation of Lycopersicon esculentum by tissue culture is known. Padmanabhan et al., (1974) Can. J. Bot. 52: 1429-1432. There is no disclosure, however, of any phenotypic variants arising by the technique. It would be desirable, therefore, to develop a method of tissue culturing Lycopersicon spp. that results in a high number of phenotypic variants.